This invention relates to a switched reluctance ("SR") motor. More particularly, the invention relates to a method and apparatus for determining rotor position of a switched reluctance motor.
SR motors have multiple poles on both the stator and the rotor. There are windings or coils wound out of the stator poles and each pair of windings on diametrically opposite stator poles are connected in series to form an electrically independent phase of the SR motor. There are no windings or magnets on the rotor. However, the rotor is made of a magnetically permeable material such as, for example, a ferrous alloy.
In order to start and run an SR motor, it is necessary to determine the position of the rotor with respect to the stator. The position of the rotor with respect to the stator establishes which phase of the stator is energized or commutated first. If the position of the rotor is not correctly determined, commutation of one of the stator phases may result in inefficient operation of the motor.
Many conventional sensors for determining rotor position are bulky, unreliable and expensive. Further, many methods used to determine rotor position require finding the peak of the current waveform.